# US 4,396,846 A · Stepping motor with rotor-positioning magnet

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- Number: US 4,396,846 A
- Document ID: US4396846A
- Status: Granted
- Kind: A
- Application number: 06/328,217
- Filed: 1981-12-07
- Granted: 1983-08-02
- Earliest claimed: 1980-12-09
- Assignees: Fabriques d'Horlogerie de Fontainemelon S.A.
- Inventors: Jean-Pierre Calame
- Web page: https://patentgrep.com/patent/US4396846A

## CPC

- G04C 13/11: with rotating armature
- H02K 37/16: having horseshoe armature cores
- G04C: ELECTROMECHANICAL CLOCKS OR WATCHES
- H02K: DYNAMO-ELECTRIC MACHINES (dynamo-electric relays H01H53/00; conversion of DC or AC input power into surge output power {H03K3/53})

## Abstract

A ring (16) of non-magnetic material is engaged in the opening bounded by the pole shoes (6,7) of a pole plate (5), between the pole shoes and the rotor (12). A magnet (18) serving to define the position of rest of the rotor is mounted on this ring, which can be accurately positioned by means of a slot (11) provided in the pole plate.

## Claims

### Claim 1

A miniature stepping motor comprising a stator having two pole shoes bounding a generally circular opening, two bearings, a rotor located in said opening and pivotally mounted on said bearings, a ring of a non-magnetic material provided with a socket and engaged in said opening between said rotor and said pole shoes and a magnet disposed in said socket, said magnet defining a position of rest of said rotor.

### Claim 2 (depends on 1)

The motor of claim 1, wherein said ring is made of plastic.

### Claim 3 (depends on 2)

The motor of claim 2, wherein said magnet is enclosed inside said plastic.

### Claim 4 (depends on 1)

The motor of claim 1, wherein said ring is made of a conductive material.

### Claim 5 (depends on 1)

The motor of claim 1, further comprising means for accurately positioning said ring with respect to said stator.

### Claim 6 (depends on 5)

The motor of claim 5, wherein said positioning means comprises a lug provided on said ring and a recess provided in the stator for receiving said lug.

### Claim 7 (depends on 6)

The motor of claim 6, wherein said magnet is mounted in said lug.

### Claim 8 (depends on 1)

The motor of claim 1, wherein one of said bearings is integral with said ring.

### Claim 9 (depends on 1)

The motor of claim 1, wherein said pole shoes are integral with each other.